Page 09 19. Which of the following is a structural formula for glycerol? A CH2 CH2 OH CH2OH B CH2OH CH2OH C CH2OH CH2COOH CHOH D CH2 CHOH OH CH2OH 20. Which line in the table best describes the effect of adding a catalyst to the following reaction? 4NH3(g) + 5O2(g) Ý 4NO(g) + 6H2O(g) ΔH = −ve Position of equilibrium Rate of forward reaction A unchanged unchanged B unchanged increased C moves to right unchanged D moves to right increased [END OF SECTION 1. NOW ATTEMPT THE QUESTIONS IN SECTION 2 OF YOUR QUESTION AND ANSWER BOOKLET.] Page 10 [BLANK PAGE] DO NOT WRITE ON THIS PAGE Page 11 [BLANK PAGE] DO NOT WRITE ON THIS PAGE Page 12 [BLANK PAGE] DO NOT WRITE ON THIS PAGE H FOR OFFICIAL USE Fill in these boxes and read what is printed below. Number of seat Town © Mark Full name of centre Forename(s) Surname Scottish candidate number Date of birth Year Day Month National Qualications 2017 Total marks — 100 SECTION 1 — 20 marks Attempt ALL questions. Instructions for the completion of Section 1 are given on Page 02. SECTION 2 — 80 marks Attempt ALL questions. You may refer to the Chemistry Data Booklet for Higher and Advanced Higher. Write your answers clearly in the spaces provided in this booklet. Additional space for answers and rough work is provided at the end of this booklet. If you use this space you must clearly identify the question number you are attempting. Any rough work must be written in this booklet. You should score through your rough work when you have written your final copy. Use blue or black ink. Before leaving the examination room you must give this booklet to the Invigilator; if you do not, you may lose all the marks for this paper. X713/76/01 MONDAY, 8 MAY 9:00 AM – 11:30 AM A/PB Chemistry Section 1 — Answer Grid and Section 2 Page 02 SECTION 1 — 20 marks The questions for Section 1 are contained in the question paper X713/76/02. Read these and record your answers on the answer grid on Page 03 opposite. Use blue or black ink. Do NOT use gel pens or pencil. 1. The answer to each question is either A, B, C or D. Decide what your answer is, then fill in the appropriate bubble (see sample question below). 2. There is only one correct answer to each question. 3. Any rough working should be done on the additional space for answers and rough work at the end of this booklet. Sample Question To show that the ink in a ball-pen consists of a mixture of dyes, the method of separation would be: A fractional distillation B chromatography C fractional crystallisation D filtration. The correct answer is B — chromatography. The answer B bubble has been clearly filled in (see below). A B C D Changing an answer If you decide to change your answer, cancel your first answer by putting a cross through it (see below) and fill in the answer you want. The answer below has been changed to D. A B C D If you then decide to change back to an answer you have already scored out, put a tick (3) to the right of the answer you want, as shown below: A B C D or A B C D Page 03 A B C D 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 SECTION 1 — Answer Grid [Turn over Page 04 [BLANK PAGE] DO NOT WRITE ON THIS PAGE Page 05 [Turn over for next question DO NOT WRITE ON THIS PAGE Page 06 MARKS DO NOT WRITE IN THIS MARGIN SECTION 2 — 80 marks Attempt ALL questions 1. The elements sodium to argon make up the third period of the Periodic Table. Na Mg Al Si P S Cl Ar (a) Name the element from the third period that exists as a covalent network. (b) Ionisation energy changes across the period. (i) Explain why the first ionisation energy increases across the period. (ii) Write an equation, including state symbols, for the second ionisation energy of magnesium. (iii) The table shows the values for the first four ionisation energies of aluminium. Ionisation energies (kJ mol−1) First Second Third Fourth 578 1817 2745 11 577 Explain why there is a large difference between the third and fourth ionisation energies. 1 1 1 1 Page 07 MARKS DO NOT WRITE IN THIS MARGIN 1. (continued) (c) The boiling point of chlorine is much higher than that of argon. Explain fully, in terms of structure and the type of van der Waals forces present, why the boiling point of chlorine is higher than that of argon. 3 [Turn over Page 08 MARKS DO NOT WRITE IN THIS MARGIN 2. Reactions involving iodine are commonly used to investigate rates of reaction. (a) One reaction involves hydrogen and iodine reacting together to form hydrogen iodide. H2(g) + I2(g) Ý 2HI(g) (i) This reaction is thought to occur by initially breaking bonds in one of the reactants. Explain, using bond enthalpies, which bond is more likely to break first during this reaction. (ii) The graph shows the distribution of kinetic energies of reactant molecules in the gas mixture at 300 °C. Ea Kinetic energy Number of molecules Add a second curve to the graph to show the distribution of kinetic energies at 400 °C. (An additional graph, if required, can be found on Page 35) 1 1 Page 09 MARKS DO NOT WRITE IN THIS MARGIN 2. (a) (continued) (iii) The reaction to produce hydrogen iodide is exothermic. H2(g) + I2(g) Ý 2HI(g) (A) State the effect of increasing temperature on the position of equilibrium. (B) State why changing the pressure has no effect on this equilibrium reaction. 1 1 [Turn over Page 10 MARKS DO NOT WRITE IN THIS MARGIN 2. (a) (continued) (iv) The potential energy diagram for the reaction between hydrogen and iodine is shown. Potential energy (kJ) unstable arrangement of atoms Reaction progress 2HI Ea forward = 173·2 kJ Ea backward = 182·8 kJ H2 + I2 (A) State the term for the unstable arrangement of atoms. (B) Calculate the enthalpy change, in kJ, for the forward reaction. (C) Platinum can be used as a catalyst for this reaction. State the effect that platinum would have on the activation energy for the reaction. 1 1 1 Page 11 MARKS DO NOT WRITE IN THIS MARGIN 2. (continued) (b) The reaction between iodide ions, I−(aq), and persulfate ions, S2O8 2−(aq), is used to investigate the effect of changing concentration on rate of reaction. The relative rate of the reaction is determined by mixing the reactants in a beaker and recording the time taken for the mixture to change colour. The results of the investigation are shown in the table. Experiment Concentration of I−(aq) (mol l−1) Concentration of S2O8 2−(aq) (mol l−1) Time (s) Relative rate (s−1) 1 0·04 0·05 241 0·00415 2 0·06 0·05 180 0·00556 3 0·08 0·05 0·00819 4 0·1 0·05 103 0·00971 (i) The instructions state that a dry beaker must be used for each experiment. Suggest a reason why the beaker should be dry. (ii) Calculate the time, in seconds, for the reaction in experiment 3. (iii) Explain why decreasing the concentration of iodide ions lowers the reaction rate. 1 1 1 [Turn over Page 12 MARKS DO NOT WRITE IN THIS MARGIN 3. The leaves of the rhubarb plant are considered poisonous because they contain high levels of oxalic acid. Oxalic acid is a white, water-soluble solid. It is a dicarboxylic acid that has the structural formula shown. C C O O O O H H Oxalic acid reacts with bases to form salts. It can also be oxidised by strong oxidising agents to form carbon dioxide gas. The oxidation equation for oxalic acid is shown. H2C2O4 ↓ 2CO2 + 2e− + 2H+ Using your knowledge of chemistry, comment on how the mass of oxalic acid in a rhubarb leaf could be determined. 3 Page 13 MARKS DO NOT WRITE IN THIS MARGIN 4. Pentyl butanoate is responsible for some of the flavour in apricots and strawberries. H C C C C C O C C C C H H H H H H H H H H H H H H H H H O (a) Hydrolysis of pentyl butanoate using sodium hydroxide produces an alcohol and the salt of the carboxylic acid. (i) Name the alcohol that would be formed when pentyl butanoate is hydrolysed. (ii) Draw a structural formula for the sodium salt of the carboxylic acid that would be formed. (b) Fats and oils belong to the same class of compounds as pentyl butanoate. (i) Name this class of compounds. (ii) When a fat is hydrolysed using sodium hydroxide, sodium salts of fatty acids are produced. State a use for sodium salts of fatty acids. 1 1 1 1 [Turn over Page 14 MARKS DO NOT WRITE IN THIS MARGIN 4. (b) (continued) (iii) Hydrolysis of fats using hydrochloric acid produces fatty acids. Stearic acid is a fatty acid that can be made from hydrolysis of beef fat. It is a fuel sometimes found in fireworks. During combustion, stearic acid (C17H35COOH) produces 623 kJ of energy per mole of CO2 produced. C17H35COOH + 26O2 ↓ 18CO2 + 18H2O mass of one mole = 284 g Calculate the energy released, in kJ, by combustion of 10 grams of stearic acid. 2 Page 15 MARKS DO NOT WRITE IN THIS MARGIN 5. Sulfur dioxide is a colourless, toxic gas that is soluble in water and more dense than air. (a) One laboratory method for preparation of sulfur dioxide gas involves adding dilute hydrochloric acid to solid sodium sulfite. The sulfur dioxide gas produced is dried by bubbling the gas through concentrated sulfuric acid. The sulfur dioxide gas can then be collected. collecting gas drying gas sodium sulfite flask dilute hydrochloric acid tap funnel (i) Complete the diagram by drawing: in the first box, apparatus suitable for drying the sulfur dioxide gas; in the second box, apparatus suitable for collecting the gas. (An additional diagram, if required, can be found on Page 35) 2 [Turn over Page 16 MARKS DO NOT WRITE IN THIS MARGIN 5. (a) (continued) (ii) 0·40 g of sodium sulfite, Na2SO3, is reacted with 50 cm3 of dilute hydrochloric acid, concentration 1·0 mol l−1. Na2SO3(s) + 2HCl(aq) ↓ H2O(ℓ) + 2NaCl(aq) + SO2(g) mass of one mole = 126·1 g Show, by calculation, that sodium sulfite is the limiting reactant. (b) Another reaction that produces sulfur dioxide gas involves combustion of carbon disulfide in the reaction shown. CS2(ℓ) + 3O2(g) ↓ CO2(g) + 2SO2(g) Calculate the enthalpy change, in kJ mol−1, for this reaction using the following information. C(s) + O2(g) ↓ CO2(g) ΔH = −393·5 kJ mol−1 S(s) + O2(g) ↓ SO2(g) ΔH = −296·8 kJ mol−1 C(s) + 2S(s) ↓ CS2(ℓ) ΔH = +87·9 kJ mol−1 2 2 Page 17 MARKS DO NOT WRITE IN THIS MARGIN 5. (continued) (c) The graph shows results for an experiment to determine the solubility of sulfur dioxide in water. 15 20 Temperature (°C) 50 250 150 5 0 200 100 0 Solubility of SO2 (g l−1) 10 (i) Determine the solubility of sulfur dioxide, in g l−1, in water at 10 °C. (ii) Information about sulfur dioxide and carbon dioxide is shown in the table. Shape of molecule Electronegativity difference between elements Solubility in water at 25 °C (g l−1) carbon dioxide linear O C O 1·0 1·45 sulfur dioxide bent O S O 1·0 94 Explain fully why carbon dioxide is much less soluble in water than sulfur dioxide is in water. 1 2 [Turn over Page 18 MARKS DO NOT WRITE IN THIS MARGIN 6. A student was carrying out an investigation into alcohols, aldehydes and ketones. (a) The student was given three alcohols labelled as A, B and C. These alcohols were all isomers with the formula C4H9OH. (i) Draw a structural formula for the secondary alcohol with the formula C4H9OH. (ii) The student set up the following experiment. C B A Hot water bath 10 cm3 of acidified dichromate solution + 2 cm3 of alcohol Alcohol Observation A Colour change B No change C Colour change (A) Suggest why a water bath is an appropriate method of heating the reaction mixture. (B) Describe the colour change that would have been observed with alcohols A and C. (C) Alcohol B is not oxidised. State the type of alcohol which cannot be oxidised by acidified dichromate solution. 1 1 1 1 Page 19 MARKS DO NOT WRITE IN THIS MARGIN 6. (a) (continued) (iii) The student set up a second experiment with alcohol A. wet pH paper held in the vapour loose plug of ceramic wool copper(II) oxide heat alcohol and ceramic wool loose plug of ceramic wool Hot copper(II) oxide is an oxidising agent. (A) When alcohol A (C4H9OH) is oxidised the product turns the pH paper red. Suggest a name for the product. (B) Complete the ion-electron equation for the oxidation reaction. C4H9OH ↓ C4H8O2 1 1 [Turn over Page 20 MARKS DO NOT WRITE IN THIS MARGIN 6. (continued) (b) The student found the following information about the boiling points of some aldehydes. Aldehyde Molecular formula Boiling point (°C) H C C C C C H H H H H H H H O H C5H10O 102 H C C C C C C H H H H H O H H H H H H C6H12O 130 H C C C C C C H H H H H O H H H C H H H H H C7H14O 153 H C C C C H H H H H CH3 O H C5H10O 95 H C C C H CH3 H CH3 O H C5H10O 75 H C C C C C H H H H H H H O H CH3 C6H12O 119 H C C C C H H CH3 H H CH3 O H C6H12O 111 (i) Name the aldehyde that has a boiling point of 119 °C. (ii) Predict the boiling point, in °C, of the following molecule. C C C C C C C H H H H H H H H H H H H O H C H H H 1 1 Page 21 MARKS DO NOT WRITE IN THIS MARGIN 6. (b) (continued) (iii) Using information from the table, describe one way in which differences in structure affect the boiling point of isomeric aldehydes. (iv) State what would be observed when an aldehyde is gently heated with Tollens’ reagent. (c) Ketones contain a carbonyl group. Name the type of intermolecular interaction between ketone molecules. 1 1 1 [Turn over Page 22 MARKS DO NOT WRITE IN THIS MARGIN 7. Some people take iron tablets as a dietary supplement. Iron tablets may contain iron(II) sulfate. (a) A student was investigating the iron(II) content of iron tablets. A work card gave the following instructions for preparing an iron tablet solution. 1. Add five iron tablets to about 50 cm3 of dilute sulfuric acid in a small beaker and stir to dissolve. 2. Transfer quantitatively to a 100 cm3 volumetric flask. 3. Make up the solution to the graduation mark on the volumetric flask. 4. Stopper the flask and then invert it to mix the solution. To ‘transfer quantitatively’ means that all of the iron tablet solution must be transferred into the volumetric flask. Describe how this is carried out in practice. (b) The concentration of iron(II) ions (Fe2+) in this iron tablet solution can be determined by a redox titration with permanganate (MnO4 −) solution. 5Fe2+(aq) + 8H+(aq) + MnO4 −(aq) ↓ 5Fe3+(aq) + Mn2+(aq) + 4H2O(ℓ) (i) Suggest why it is not necessary to add an indicator to this titration. 1 1 Page 23 MARKS DO NOT WRITE IN THIS MARGIN 7. (b) (continued) (ii) Suggest why the titration must be carried out under acidic conditions. (iii) Three 25·0 cm3 samples of the iron tablet solution were titrated with a standard solution of 0·020 mol l−1 permanganate (MnO4 −). The results are shown below. Sample Volume of permanganate (cm3) 1 14·9 2 14·5 3 14·6 (A) State why the volume of permanganate used in the calculation was taken to be 14·55 cm3, although this is not the average of the three titres in the table. (B) Calculate the concentration, in mol l−1, of iron(II) ions in the iron tablet solution. 5Fe2+(aq) + 8H+(aq) + MnO4 −(aq) ↓ 5Fe3+(aq) + Mn2+(aq) + 4H2O(ℓ) 1 1 3 [Turn over Page 24 MARKS DO NOT WRITE IN THIS MARGIN 7. (b) (iii) (continued) (C) State what is meant by the term standard solution. (D) Name an appropriate piece of apparatus which could be used to measure 25·0 cm3 samples of iron tablet solution. (c) In a different experiment, five iron tablets were found to contain 0·00126 moles of iron(II) ions. Calculate the average mass, in mg, of iron present in one tablet. (d) It is recommended an adult female takes in 14·8 mg of iron per day. 100 g of a breakfast cereal contains 12·0 mg of iron. Calculate the percentage of the recommended daily amount of iron provided for an adult female by a 30 g serving. 1 1 1 2 Page 25 MARKS DO NOT WRITE IN THIS MARGIN 8. Skin care products contain a mixture of polar covalent, non-polar covalent and ionic compounds. The compounds need to stay mixed within the product. Skin care products also need to spread easily and remain on the skin for a period of time, as well as provide physical and chemical protection from the sun. In order to do this, skin care products contain a range of chemicals including water, fats and oils, antioxidants, minerals and sun block. Using your knowledge of chemistry, explain the role of different chemicals in skin care products. 3 [Turn over Page 26 [BLANK PAGE] DO NOT WRITE ON THIS PAGE Page 27 MARKS DO NOT WRITE IN THIS MARGIN 9. Dishwasher tablets contain chemicals which remove dirt from dishes. (a) Dishwasher tablets include detergents. These molecules act like soaps to allow mixing of fat-soluble dirt and water. (i) During the cleaning process, the detergent molecules combine with fat-soluble dirt. A simplified diagram of a detergent molecule is shown. covalent tail ionic head Complete the diagram below to show how detergent molecules combine with fat-soluble dirt. fat-soluble dirt (An additional diagram, if required, can be found on Page 36) (ii) State the term used to describe the non-polar, hydrocarbon tail of a detergent molecule. 1 1 [Turn over Page 28 MARKS DO NOT WRITE IN THIS MARGIN 9. (continued) (b) Dishwasher tablets produce the bleach hydrogen peroxide, H2O2. One action of this oxidising agent is to oxidise food. (i) Suggest another action of the bleach produced by the dishwasher tablets. (ii) Hydrogen peroxide decomposes to form water and oxygen. 2H2O2(ℓ) ↓ 2H2O(ℓ) + O2(g) A dishwasher tablet produces 0·051 g of hydrogen peroxide (mass of one mole = 34 g). Calculate the volume of oxygen that would be produced when 0·051 g of hydrogen peroxide decomposes. Take the volume of 1 mole of oxygen gas to be 24 litres. (c) Enzymes are commonly added to dishwasher tablets. These are used to break down proteins. (i) The proteins are broken down into small, water-soluble molecules. Name the small, water-soluble molecules made when proteins are broken down completely. 1 3 1 Page 29 MARKS DO NOT WRITE IN THIS MARGIN 9. (c) (continued) (ii) The structure of a section of protein chain found in egg white is shown. C C N C C N C C N C C N O H H O H O H O H CH CH2 CH2 CH2 NH C H2N NH H H CH2 SH H H H3C CH2 CH3 (A) Name the functional group circled. (B) Draw a structural formula for one of the molecules that would be made when this section of egg white protein chain is completely broken down. (iii) As part of the program in the dishwasher, the conditions in the dishwasher change so that the enzyme molecules no longer work because they change shape. (A) State the term used to describe the change in shape of enzyme molecules. (B) Suggest a change in conditions which would cause the enzyme molecules to change shape. 1 1 1 1 [Turn over Page 30 MARKS DO NOT WRITE IN THIS MARGIN 9. (continued) (d) A bleach activator is frequently added to dishwasher tablets to speed up the bleaching reaction. One common bleach activator is TAED. TAED could be produced in a process which involves a number of stages. (i) The first stage in producing TAED is shown below. N H H H O C O CH3 + (CH2)2 N H H N C H O CH3 + (CH2)2 N H H O C C O O H3C CH3 ethylene diamine acetic anhydride Suggest a name for this type of reaction. 1 Page 31 MARKS DO NOT WRITE IN THIS MARGIN 9. (d) (continued) (ii) The final stage in the process producing TAED is shown below. N C H H O TAED C O O O O CH3 CH3 + + (CH2)2 N C C O C C O O H3C H3C H3C CH3 Draw a structural formula for TAED. 1 [Turn over Page 32 MARKS DO NOT WRITE IN THIS MARGIN 10. Essential oils from the lavender plant are used in aromatherapy. (a) Gas chromatography can be used to separate and identify the organic compounds in lavender oils. Chromatogram 1 - Lavender oil A 24 20 22 18 Retention time (minutes) (6) (5) (3) (4) (2) (1) 16 14 Peak Component Component peak area 1 1,8-cineole 7432 2 linalool 31 909 3 camphor 7518 4 linalyl acetate 27 504 5 geranyl acetate 3585 6 farnesene 1362 Total peak area    =        79 310 The relative concentration of each component can be calculated using the following formula. Relative concentration = Component peak area 100 (%) Total peak area × (i) Calculate the relative concentration of linalool in lavender oil A. 1 Page 33 MARKS DO NOT WRITE IN THIS MARGIN 10. (a) (continued) (ii) Different varieties of lavender oils have different compositions. Chromatogram 2 – Lavender oil B Retention time (minutes) 24 22 20 18 16 14 Identify the component found in lavender oil A that is missing from lavender oil B. (b) A brand of mouthwash contains the component 1,8-cineole at a concentration of 0·92 mg per cm3. The cost of 1 kg of 1,8-cineole is £59·10. Calculate the cost, in pence, of 1,8-cineole that is present in a 500 cm3 bottle of this brand of mouthwash. 1 2 [Turn over for next question Page 34 MARKS DO NOT WRITE IN THIS MARGIN 10. (continued) (c) The component molecules found in lavender oils are terpenes or terpenoids. (i) A chiral carbon is a carbon atom attached to four different atoms or groups of atoms. An example is shown below. H3C C H Cl C2H5 Chiral carbon atom A molecule of the terpenoid linalool has a chiral carbon. Linalool has the following structure. C C C C C H H CH3 H H O H H C C H3C H CH3 H H Circle the chiral carbon atom in the linalool structure. (An additional diagram, if required, can be found on Page 36) (ii) Farnesene is a terpene consisting of three isoprene units (2-methylbuta-1,3-diene) joined together. Write the molecular formula of farnesene. [END OF QUESTION PAPER] 1 1 Page 35 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK ADDITIONAL DIAGRAM FOR USE IN QUESTION 2 (a) (ii) Ea Kinetic energy Number of molecules ADDITIONAL DIAGRAM FOR USE IN QUESTION 5 (a) (i) collecting gas drying gas sodium sulfite flask dilute hydrochloric acid tap funnel Page 36 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK ADDITIONAL DIAGRAM FOR USE IN QUESTION 9 (a) (i) fat-soluble dirt ADDITIONAL DIAGRAM FOR USE IN QUESTION 10 (c) (i) C C C C C H H CH3 H H O H H C C H3C H CH3 H H Page 37 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK Page 38 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK Page 39 [BLANK PAGE] DO NOT WRITE ON THIS PAGE Page 40 [BLANK PAGE] DO NOT WRITE ON THIS PAGE